import React, { Component } from "react";
// import { connect } from 'react-redux';

export default class index extends Component {
  state = { count: 0 };

  increment = () => {
    const { value } = this.selectNumber;
    const { count } = this.state;
    this.setState({ count: count + value * 1 });
  };
  delIncrement = () => {
    const { value } = this.selectNumber;
    const { count } = this.state;
    this.setState({ count: count - value * 1 });
  };
  incrementIfOdd = () => {
    const { value } = this.selectNumber;
    const { count } = this.state;
    if (count % 2 !== 0) {
      this.setState({ count: count + value * 1 });
    }
  };
  incrementAsync = () => {
    setTimeout(() => {
        const { value } = this.selectNumber;
        const { count } = this.state;
        this.setState({ count: count + value * 1 });
    }, 1000)
  };

  render() {
    return (
      <div>
        <h1>当前求和为：{this.state.count}</h1>
        <select ref={(c) => (this.selectNumber = c)}>
          <option value="1">1</option>
          <option value="2">2</option>
          <option value="3">3</option>
          <option value="4">4</option>
        </select>
        &nbsp;
        <button onClick={this.increment}>+</button> &nbsp;
        <button onClick={this.delIncrement}>-</button> &nbsp;
        <button onClick={this.incrementIfOdd}>当前求和为奇数再加</button>{" "}
        &nbsp;
        <button onClick={this.incrementAsync}>异步求和</button>
      </div>
    );
  }
}
